Process of transferring piezoelectric layer onto carrier substrate

Abstract

The invention relates to a process for transferring a piezoelectric layer (3) onto a carrier substrate (6). The process comprises providing a donor substrate (40) comprising a heterostructure (4) comprising a piezoelectric substrate (3) bonded to a handle substrate (2), and a polymerized adhesive layer (10) located at an interface between the piezoelectric substrate (3) and the handle substrate (2). A weakened region (7) is formed in the piezoelectric substrate (3), thereby defining a piezoelectric layer (31) to be transferred. A carrier substrate (6) is provided, and a dielectric layer (8) isformed on the carrier substrate (6) and / or on the main face of the piezoelectric substrate (3). The donor substrate (40) is bonded to the carrier substrate (6), the dielectric layer (8) is located atthe bonding interface, and at a temperature of less than or equal to 300 DEG C, the donor substrate (40) is divided and separated along the weakened region (7).

Description

technical field [0001] The invention relates to a process for manufacturing a donor substrate for transferring a piezoelectric layer, and a process for transferring such a piezoelectric layer. The invention finds particular application in the manufacture of radio frequency devices, such as resonators or filters. Background technique [0002] It is known practice to fabricate radio frequency (RF) devices, such as resonators or filters, on a substrate which in turn comprises, from its bottom to its surface, a carrier substrate usually made of a semiconductor material such as silicon , electrical insulating layer and piezoelectric layer. [0003] Bulk acoustic wave (BAW) devices generally comprise a thin piezoelectric layer (ie, generally substantially less than 1 μm in thickness) and two electrodes arranged on each major face of the thin layer. An electrical signal (usually a change in voltage) applied to the electrodes is converted into an elastic wave that propagates throu...

AI Technical Summary

Problems solved by technology

[0013] First, depositing an oxide layer on a thick piezoelectric substrate makes said piezoelectric substrate substantially curved (curved), which is not very compatible with subsequent steps in a process designed for flat substrates

[0014] Furthermore, the formation of the oxide layer required for bonding is tedious and expensive

[0015] Finally, as mentioned above, heterostructures cannot be subjected to consolidation annealing due to the difference in thermal expansion coefficient between the thick piezoelectric substrate and the handle substrate.

However, without consolidation annealing, the bonding energy of the oxide layers of the two substrates remains very low, making the mechanical strength of the donor dummy substrate insufficient

Therefore, in the step of thinning the thick piezoelectric substrate, cracks may be generated at the bonding interface

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